STEVE WEBBER, PRODUCT MANAGER AT EXTERNAL INSULATION AND RENDER SPECIALIST KNAUF MARMORIT, DISCUSSES HOW TO INSULATE OLDER PROPERTIES
There are many ways to thermally upgrade an older property-loft insulation, cavity wall insulation and External Wall insulation known as EWI or ETICS (External Thermal Insulation Composite System).
Before work commences on a EWI system installation it is always best to check with the local authority planning department as EWI system can dramatically change the look and feel of a building and may require planning permission.
A check should be made with the building control department to see if a certain type of insulation maybe required, if the building, is within 1m of another building mineral fibre insulation may be required to comply with fire regulations.
If there are any large cracks in the substrate then it would be advisable to ask a structural engineer to give a report to ensure that the substrate is in a sound condition and that any potential repairs and damp issues are resolved prior to installation of a EWI system.
Other considerations would be the relocation of domestic services into the property, such as electricity, gas, telephone and satellite installations, as these are often fixed to the external walls of older properties, although some services can be boxed in to hide them, access maybe required by the utility company for maintenance.
Air vents, boiler ducts, outside taps washing lines and external lights all need to be relocated or extended to the surface of the EWI system and fixing points inserted in the system to take the newly positioned services.
Ventilation to the eaves of the soffit will need to remain open so the system may need to be terminated short of the soffit or chamfered back to allow passage of air to the loft space.
Overhangs such as parapet walls gable ends and other projections from the walls will need to be allowed for and a suitable weather tight detail designed to ensure weather tightness.
Sheds, and fences, may need to be relocated as these often abut property walls and canopies. Lean-tos and conservatories may need fabricated flashings made for them.
Window cills will need to be extended and in the case of UPVC windows the original fabricator can often provide these to suit the window system used on the property, it is important to allow an overhang to the face of the finished render system and this is generally around 35mm.
Identification of the existing damp course must be carried out as this should not be bridged by the new EWI system and should be at least 1500mm – 200mm above any surface finish such as decking or paving.
If no damp course is present, then consideration should be given to one being injected into the substrate for masonry situations, as this will be much easier at this stage before the application of the EWI system.
A U-Value calculation with a condensation risk should be carried out to establish the building’s current thermal performance and to see what effect the new EWI system would have on the building after installation as grants maybe available with the cost of thermally upgrading the building.
This calculation would also highlight any potential condensation risks that may affect the building by adding insulation to the external wall, particularly, if the cavity has been previously filled with injected insulation.
If the current property already has sand and cement render system installed or pebble dash this should be checked for potential problems, as these renders can sometimes be unsuitable for the application of a EWI system and advice should be sought from a system manufacturer’s technical department before application of a system.
Design advice and technical help should always be sought from the system supplier – designer prior to application of any system.
Knauf Marmorit supplies external insulation and manufactures its own base coats, finishes, render and scratch render for a variety of building types. The company also offers render systems for framed system solutions, façade paints, primers and insulation products.
Knauf Marmorit
Tel: 0117 982 1042
Email: steve@marmorit.co.uk
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